The Aleutian Islands of Alaska are home to a number of major volcanoes which periodically present a significant hazard to aviation. During summer of 2008, the Okmok and Kasatochi volcanoes experienced moderate eruptive events. These were followed a dramatic, major eruption of Mount Redoubt in late March 2009. The Redoubt case is extensively covered in this paper. Volcanic ash and SO2 from each of these eruptions dispersed throughout the atmosphere. This created the potential for major problems for air traffic near the ash dispersions and at significant distances downwind. The NASA Applied Sciences Weather Program implements a wide variety of research projects to develop volcanic ash detection, characterization and tracking applications for NASA Earth Observing System and NOAA GOES and POES satellites. Chemistry applications using NASA AURA satellite Ozone Monitoring System (OMI) retrievals produced SO2 measurements to trace the dispersion of volcanic aerosol. This work was complimented by advanced multi-channel imager applications for the discrimination and height assignment of volcanic ash using NASA MODIS and NOAA GOES and POES imager data. Instruments similar to MODIS and OMI are scheduled for operational deployment on NPOESS. In addition, the NASA Calipso satellite provided highly accurate measurements of aerosol height and dispersion for the calibration and validation of these algorithms and for corroborative research studies. All of this work shortens the lead time for transition to operations and ensures that research satellite data and applications are operationally relevant and utilized quickly after the deployment of operational satellite systems. Introductio

Hudnall, L. A.

Krueger, A. J.

Matus, A.

Murray, John J.

Trepte, C. r.

NASA Technical Reports Server

The detection, characterization and tracking of recent Aleutian Island 
volcanic ash plumes and the assessment of their impact on aviation 
 
Murray, John J.1, L.A. Hudnall2, A. Matus3, A.J. Krueger4, C.R. Trepte1 
 
1NASA Langley Research Center, Hampton, VA 
 2Christopher Newport University, Newport News, VA 
3Texas A&M University, College Station, TX 
4University of Maryland, Baltimore Campus, Baltimore, MD 
 
 
The Aleutian Islands of Alaska are home to a number of major 
volcanoes which periodically present a significant hazard to 
aviation. During summer of 2008, the Okmok and Kasatochi 
volcanoes experienced moderate eruptive events. These were 
followed a dramatic, major eruption of Mount Redoubt in late 
March 2009. The Redoubt case is extensively covered in this 
paper. Volcanic ash and SO2 from each of these eruptions 
dispersed throughout the atmosphere. This created the 
potential for major problems for air traffic near the ash 
dispersions and at significant distances downwind. The NASA 
Applied Sciences Weather Program implements a wide variety 
of research projects to develop volcanic ash detection, 
characterization and tracking applications for NASA Earth 
Observing System and NOAA GOES and POES satellites. 
Chemistry applications using NASA AURA satellite Ozone 
Monitoring System (OMI) retrievals produced SO2 
measurements to trace the dispersion of volcanic aerosol. This 
work was complimented by advanced multi-channel imager 
applications for the discrimination and height assignment of 
volcanic ash using NASA MODIS and NOAA GOES and 
POES imager data. Instruments similar to MODIS and OMI 
are scheduled for operational deployment on NPOESS. In 
addition, the NASA Calipso satellite provided highly accurate 
measurements of aerosol height and dispersion for the 
calibration and validation of these algorithms and for 
corroborative research studies. All of this work shortens the 
lead time for transition to operations and ensures that research 
satellite data and applications are operationally relevant and 
utilized quickly after the deployment of operational satellite 
systems.  
 
Introduction 
 
This paper provides an overview of research results using NASA Earth Observing 
System and NOAA GOES and POES satellites to detect, characterize and track volcanic 
https://ntrs.nasa.gov/search.jsp?R=20100003407 2019-08-30T08:46:05+00:00Z
ash in the atmosphere. It examines several case studies to highlight how data taken during 
recent eruptions of the Okmok, Kasatochi and Redoubt volcanoes in the Aleutian Islands 
of Alaska were used by the Alaska, Washington and Montreal Volcanic Ash Advisory 
Centers (VAAC) to assist in developing and issuing Volcanic Ash Advisories (VAA) and 
by the FAA, USGS and others to assess their impact on the National Airspace System.  
 
 
Case I: Okmok Volcano 
 
Okmok erupted on July 12, 2008. Figure 1 shows the dispersion of SO2 which is 
routinely used as a proxy for volcanic ash. The dispersion of volcanic ash from Okmok 
occurred over the northwestern United States five days after the volcano’s initial 
eruption. Figure 1 exhibits a zonal flow pattern in consonance with the prevailing 
westerlies.  
 
 
 
 
 
 
 
 
Case 2: Kasatochi Volcano 
 
Kasatochi erupted on August 7, 2008. Figure 2, below shows the complex 
dispersive pattern of SO2 four days later which evolved from a very complex, dynamic, 
mid-latitude synoptic pattern.  
 
Figure 1. SO2 as detected by Aura/OMI in the northwestern United States five days after the initial eruption of 
Okmok.  
 
 
 
 
Case 3: Mount Redoubt Volcano 
 
 
 
 
Figure 2.  SO2 as detected by Aura/OMI in North America four days after the initial eruption of Kasatochi.  
Figure 3.  The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s 
Terra satellite obtained this image of Mount Redoubt and its environs on May 5, 2009, just two days before it 
erupted explosively. There was little visible activity other than the vapor plume near the center of the image.  
Mt. Redoubt erupted explosively at 10:38 P.M. the night of Sunday, March 22, 
2009. Figure 4, below captured the eruptive plume which was estimated to reach a height 
of 50,000 feet above MSL. 
 
 
 
Figure 4.  Volcanic ash detected on March 22, 2009 in thermal infrared imagery by the Moderate 
Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite.  
 
 
Mt. Redoubt is a 3,108-meter (10,197 ft) stratovolcano located at 60.4852°N and 
152.7438°W in the Chigmit Mountains of Alaska. An eruption of Redoubt has major 
implications for the city of Anchorage, Alaska, which is situated 110 kilometers to the 
east-northeast. A volcanic eruption poses an especially large threat to aircraft flying to 
and from the airport at Anchorage. Anchorage International Airport is the cargo hub for 
Alaska Airlines and is the third largest air-cargo hub in the world (AVO, 2009). 
 
After a nearly 20-year period of dormancy, Mt. Redoubt began showing signs of activity 
again in 2008.  At 0638Z on 23 March, the AVO reported a large eruption of Mt. 
Redoubt. Between 0638Z on 23 March and 1300Z on 23 March there were a total of five 
explosive eruptions. According to the Anchorage Volcanic Ash Advisory Center, issued 
at 1725Z on 23 March, the highest ash plume may have reached 60,000 feet above mean 
sea level, based on analysis of satellite imagery (http://www.avo.alaska.edu). Most of the 
ash cloud following the eruption was suspended in the atmosphere between 25,000 and 
30,000 feet above mean sea level. At 0341Z on 24 March, the AVO recorded a sixth 
eruption, in which the National Weather Service posted a new ashfall advisory for areas 
north of the volcano. At 1312Z on 25 March, a seventh eruption of Redoubt was 
observed, although the eruptive event was much less intense than previous eruptions. The 
ash plume did not exceed 12,000 feet above mean sea level. A brief period of calm 
followed the seventh eruption as seismicity levels returned to normal. However, on the 
following day, at 1634Z on 26 March, an eighth eruptive event occurred. Local radar 
confirmed the height of the ash plume at 30,000 feet above mean sea level. At 1724Z on 
26 March the AVO reported a “major explosive event” from Mt. Redoubt. According to 
the National Weather Service, the ash plume had reached a peak height of 65,000 feet 
above mean sea level, high enough to inject volcanic ash into the stratosphere. Several 
minor steam and ash emissions continued throughout the following days, with the last 
reported ash emission occurring on 4 April 2009. 
 
Volcanic ash was tracked using AURA/OMI SO2 column measurements on 23, 24, and 
25 March 2009. Corresponding times were matched with CALIPSO backscatter profiles, 
geopotential height plots, and HYSPLIT forward model trajectories. The CALIPSO 
backscatter profiles show the vertical cross section of the atmosphere along an orbital 
path. The geopotential height plots were reviewed to assess the geostrophic wind flow at 
various pressure levels in the atmosphere. Finally, HYSPLIT forward model trajectories 
initialized at Mt. Redoubt show the expected dispersion of particles in the atmosphere at 
a given altitude and time period. For this study the 72-hour model run was initialized at 
06Z on 23 March 2009, with a new trajectory created every 8 hours. The purpose of 
generating multiple trajectories was to simulate the continued volcanic activity of 
Redoubt during the hours and days following the initial eruption. Through analysis of 
these data the level in the atmosphere was estimated in which SO2 dispersion, and by 
extension ash dispersion, likely occurred on 23, 24, and 25 March 2009 (Matus and 
Hudnall, 2009). 
 
 
 
Figure 5: CALIPSO backscatter profiles with OMI SO2 column measurements 
 
Results indicate that a complex dispersion of volcanic ash resulted from the eruption of 
Mt. Redoubt. The altitudes of ash dispersion were estimated on 23, 24, and 25 March 
2009 using CALIPSO backscatter profiles, geopotential height plots, HYSPLIT forward 
model trajectories, and SO2 column measurements. Figure 5 displays a Google Earth 
visualization of CALIPSO profiles for 23, 24, and 25 March overlaid with OMI SO2 
column measurements over the corresponding time periods. On 23 March 2009, 
CALIPSO detected a cloud/aerosol feature at or below 10 km, geopotential heights 
showed ash dispersion supported by atmospheric pattern between 400 and 200 mb (see 
Figure 6), and HYSPLIT forward trajectories supported ash dispersion at or below 11 
km. The majority of the ash plume likely remained at approximately 8 km, although 
reports from the National Weather Service indicate that the initial plume may have 
reached 18 km (60,000 ft). 
 
 
 
Figure 6: Geopotential height field plot at 300mb for 23 March 2009 (NCEP) 
 
 
On 24 March 2009, CALIPSO detected a cloud/aerosol feature at or below 9 km with 
additional features detected at 10 km and 16 km, and geopotential heights showed most 
of the ash dispersion supported by atmospheric pattern between 500 and 300 mb and ash 
dispersion near Hudson Bay supported by atmospheric pattern at 700 mb. HYSPLIT 
forward trajectories supported ash dispersion at or below 11 km. Most ash was entrained 
in a passing low pressure system at around 8 km. It is possible that some ash was detected 
by CALIPSO at higher altitudes (10 km and 16 km). Near Hudson Bay, however, 
atmospheric patterns suggest ash dispersion at approximately 3 km. 
 
On 25 March 2009, CALIPSO detected a cloud/aerosol feature at or below 8km with 
additional features detected at 14 km, geopotential heights showed most of the ash 
dispersion supported by atmospheric pattern between 500 and 150 mb, and HYSPLIT 
forward trajectories supported ash dispersion between 11 km and 15 km. Much of the ash 
plume remaining was detected at higher altitudes three days following the eruption. The 
stratospheric ash plume was likely located 14 km above mean sea level, as detected by 
CALIPSO. 
 
According to the Alaska Volcano Observatory, there were 26 reported volcanic eruptions 
from Mt. Redoubt during 2009. Steam emission commenced at 2100Z on 15 March. The 
released steam was a precursor to the first major ash eruption, which occurred at 0638Z 
on 23 March. The eruptive period of Redoubt lasted for nearly two weeks. Most eruptions 
during this period produced minor ash and steam plumes; a few eruptions posed more 
serious problems, especially for aviation. The most recent ash emission occurred at 
1358Z on 4 April 2009.  
 
Commercial aviation was most notably disrupted by two major explosive events from Mt. 
Redoubt: at 0638Z on 23 March and at 1724Z on 26 March. The first five eruptions, 
occurring over a period of 6 hours on 23 March, caused 35 flight cancellations from 
Anchorage International Airport. The eruptions took place at night between 10:38 pm and 
4:31 am local time, visibility of the ash plume would have been increasingly difficult for 
pilots. Four minor eruptions ensued, with considerably less impact on aviation. An 
eruption at 1724Z on 26 March, with an ash plume exceeding 65,000 feet above mean sea 
level, resulted in an additional 10 flight cancellations. By the time the eruptions had 
subsided in April, Alaska Airlines had cancelled 295 flights and disrupted the flights of 
over 20,000 passengers (The News Tribune, 2009). 
 
 
Figure 7: Volcanic ash advisory issued on 23 March 2009 (VAAC Anchorage) 
 
The Anchorage Volcanic Ash Advisory issued on 23 March 2009 is displayed in Figure 
7. The gray polygons reveal areas of greatest risk for encountering volcanic ash for the 
given time period. The four panels correspond to forecast times of 1609Z on 23 March, 
2325Z on 23 March, 0525Z on 24 March, and 1125Z on 24 March. The extent of the ash 
advisory is determined by a variety of observational criteria including GOES satellite 
imagery, AVO reports, pilot reports, radar, and forecast models. Volcanic Ash Advisories 
are used by airlines to assess the risk in flying certain flight routes after a volcanic 
eruption. The issued ash advisory may influence the decision by airlines to delay or 
cancel flights. 
 
This graphical Volcanic Ash Advisory was the only one publically available during the 
eruption of Mt. Redoubt. The ash advisory suggests that most of the ash dispersion 
occurred to the east of the volcano with some ash dispersion occurring to the west of the 
volcano. Actual SO2 column measurements reveal nearly all ash dispersion occurred to 
the east of the volcano. As a result, the issued ash advisory covered a much larger extent 
than necessary. It is possible that flights may have been rerouted, delayed, or cancelled as 
a result of the larger ash advisory. 
 
Deveral factors may have led the Anchorage Volcanic Ash Advisory Center to issue a 
Volcanic Ash Advisory extending to the west of the volcano. At the time of the issuance 
at 1725Z on 23 March, volcanic ash below FL200 was detected moving north and west of 
the volcano whereas volcanic ash above FL200 was detected moving north and east of 
the volcano. In addition to observational reports, model runs may also influence the 
volcanic ash advisory extent. A particular model run from the HYSPLIT forward 
trajectory model supports a larger extent of the Volcanic Ash Advisory. Initialized at the 
time of the initial eruption, the model indicates that air parcels above 5 kilometers AMSL 
will disperse eastward and air parcels below 5 kilometers AMSL will disperse westward. 
Since the majority of actual ash dispersion occurred east of Mt. Redoubt, perhaps the ash 
plume reached a higher altitude than expected. This would potentially account for model 
output of ash dispersion west of Mt. Redoubt and, ultimately, a larger extent of the ash 
advisory. 
 
The inability to fly not only creates complications for travelers, but also disrupts air 
transport of food and prescription drugs into the state of Alaska. The economic impact of 
the delayed transport of goods is substantially significant. Following an ash-rich eruption 
at 2329Z on 28 March, tephra was reported falling out at Valdez and Anchorage. 
Precautionary measures forced airlines to ground flights at Anchorage for extended 
hours. Due to the long-term dispersion of volcanic ash, Mt. Redoubt’s eruptions caused 
problems for Anchorage International Airport which lasted for several weeks following 
the eruption. 
 
 
The aviation industry was well prepared for the eruption of Mt. Redoubt. Communication 
with the Alaska Volcano Observatory allowed Alaska Airlines to take preparatory 
measures weeks prior to the initial eruption. No ash encounters with aircraft resulted from 
the 2009 Mt. Redoubt eruption. Despite having adequate knowledge of ash dispersion, 
many airlines incurred significant economic costs as a result of the 2009 Redoubt 
eruption. Hundreds of flights had been delayed or cancelled following the eruption, 
particularly after the 23 March eruption. OMI satellite measurements reveal the pattern of 
ash dispersion and areas where airspace was most at risk. Much of the ash cloud had 
drifted north and east of Anchorage before turning southward through British Columbia. 
Considering that quite often the upper level winds over Anchorage are steered downwind 
of Mt. Redoubt, conditions were relatively favorable for pilots in Anchorage. 
Volcanic Ash Advisories are frequently used by airlines to assess the risk of using certain 
commercial flight routes. Pilots may be advised not to fly in regions as indicated by 
Volcanic Ash Advisories. The Volcanic Ash Advisory issued on 23 March (Figure 7) 
shows an extensive region of threatened airspace surrounding Mt. Redoubt. Although 
OMI SO2 column measurements reveal upper level winds transported the ash plume to 
the north and east, the issued Volcanic Ash Advisory indicates areas to the south and 
west of Redoubt at risk for volcanic ash. Aircraft may have avoided flying through 
regions south and west of Redoubt due to the ash advisory issued by the Anchorage 
Volcanic Ash Advisory Center. However, there was a minimal risk for ash in these 
regions and therefore flight delays or cancellations in these areas would have resulted in 
unnecessary economic costs. Improved communication between Volcanic Ash Advisory 
Centers and ash detection agencies will improve the quality of information ultimately 
disseminated to pilots. Since the issue of ash avoidance is primarily an issue of economic 
implications, an investment in preparing for volcanic encounters would yield high returns 
for the airline industry over the long term. 
 
 
Acknowledgements 
 
This paper is an overview of work performed by my Langley Aerospace Research 
Summer Scholars (LARSS) Program students Lauren Hudnall and Alexander Matus 
during 2008 and 2009. The OMI retrievals and images were produced at UMBC by Arlin 
Krueger’s excellent volcanic ash research group under a grant from the NASA Applied 
Sciences ROSES Program. Coincident Calipso retrievals and combined OMI/Calipso 
images were produced at NASA Langley by Alex Matus. 
 
 
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The Detection, Characterization and Tracking of Recent Aleutian Island Volcanic Ash Plumes and the Assessment of Their Impact on Aviation

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